Please refer to FIG. 1, which shows a conventional galvanic cell 1a. The galvanic cell 1a includes a first trough T1 and a second trough T2, wherein the first trough T1 is separated from the second trough T2. The first trough T1 contains a first salt solution AQ1 for soaking a first metal M1, and the second trough T2 contains a second salt solution AQ2 for soaking a second metal M2. The first metal M1 and the second metal M2 are electrically connected to a load 2, and the first trough T1 is connected to the second trough T2 via a salt bridge SB. If the first metal M1 serves as the anode, i.e. the oxidizing terminal, it loses the electron e−. The electron e− reaches the second metal M2 via the load 2. The first metal M1 is stored in the first salt solution AQ1 in the type of the cation. Because the second metal M2 obtains the electron, the metal cation in the second salt solution AQ2 is separated out and adhered to the second metal M2. The anion is generated in the second trough T2, and interacts with the cation of the first metal M1 via the salt bridge SB.
Please refer to FIG. 2, which shows another conventional galvanic cell 1b. The galvanic cell 1b includes a third trough T3 and a fourth trough T4, wherein the third trough T3 is separated from the fourth trough T4 by an ion penetrating element 13. The third trough T3 contains a third salt solution AQ3 for soaking a third metal M3, and the fourth trough T4 contains a fourth salt solution AQ4 for soaking a fourth metal M4. If the third metal M3 serves as the anode, i.e. the oxidizing terminal, it loses the electron e−. The electron e− reaches the fourth metal M4 via the load 2. The third metal M3 is stored in the third salt solution AQ3 in the type of the cation. Because the fourth metal M4 obtains the electron, the metal cation in the fourth salt solution AQ4 is separated out and adhered to the fourth metal M4. The anion is generated in the fourth trough T4, and passes through the ion penetrating element 13 to reach the third trough T3.
The conventional galvanic cells are described above. However, besides the above-mentioned galvanic cells, other galvanic cells can use other metals to serve as the electrodes, or use other salt solutions to serve as the electrolytes, or add an auxiliary agent to the electrolyte. If the electrolyte or the metal electrode is exhausted, or the voltage is insufficient, it means that the cell is unserviceable. At this time, the components of the cell need to be replaced, or the entire cell needs to be replaced, or a reverse charge needs to be performed to restore the cell to the previous undischarged state. In terms of replacing the components of the cell, a lot of inconveniences are generated. In terms of replacing the entire cell, the cost of dealing with the waste cell is generated. Therefore, besides the purchasing and replacing costs, using the galvanic cell also results in an extremely high environmental cost.
For solving the above-mentioned issues, the fuel cell is invented. Please refer to FIG. 3, which shows a conventional fuel cell 1C. The fuel cell 1C includes a cell trough 10. The cell trough 10 has a cathode 11 and an anode 12. The cathode 11 is separated from the anode 12 by an ion penetrating element 13 so that the cell trough 10 is divided into a cathode trough 10a and an anode trough 10b. The oxygen 11G is transported to the cathode trough 10a, and the hydrogen gas 12G is transported to the anode trough 10b. Through the functions of the electrolytic substance and the anode 12 in the cell trough 10, the hydrogen gas 12G is oxidized to release the electron, and then the electron reaches an external load 2. The hydrogen ion without the electron, i.e. the proton, passes through the ion penetrating element 13 to reach the cathode trough 10a. At this time, the electron also reaches the cathode 11, and the oxygen 11G is also transported to the cathode trough 10a so that the proton, the electron, and the oxygen 11G are combined to become the water W, with the cooperation of the cathode 11.
The conventional fuel cell is described above. However, the above-mentioned fuel (reductant) and oxidizer can be replaced by other fuels and oxidizers. By carefully selecting the fuel (reductant) and oxidizer of the fuel cell, the environmental damage resulting from the waste product generated by the fuel cell can be reduced. In FIG. 3, the fuel is the hydrogen gas, and the oxidizer is the oxygen. The fuel cell 1C of FIG. 3 is advantageous in that the waste product generated by the fuel cell 1C is only the water, which has a minimum impact on the environment. The conventional method for using the fuel and oxidizer is to use the heat engine to covert the energy generated by the combustion of the fuel and oxidizer via the mechanical structure so as to drive the generator to generate power. For example, the heat engine can be an internal combustion engine or an external combustion engine. For example, the internal combustion engine can be a gasoline and diesel engine or a gas turbine, and the external combustion engine can be a steam turbine. However, in the fuel cell, the flow of the electron reacted between the fuel and the oxidizer directly serves as the power source. Theoretically, the fuel cell has a maximum efficiency and a minimum overall volume. Besides, the fuel cell is convenient to use.
However, the fuel (reductant) or the oxidizer used in the fuel cell is not easy to be stored. For example, the hydrogen gas serving as the fuel and the oxygen serving as the oxidizer need to be stored in a high-pressure bottle to enhance the capacity, or they are easy to be exhausted. Besides, other types of fuels or oxidizers may be limited to other conditions due to their higher activities, or will discharge the greenhouse gas. Therefore, a new technology is needed in this field to break through these limitations so that the fuel cell can be widely used.
In order to overcome the drawbacks in the prior art, a mediator-type photocell system is provided. The particular design in the present invention not is only solves the problems described above, but also is easy to be implemented. Thus, the present invention has the utility for the industry.